This invention relates to catheters used for delivering medical devices. The catheter incorporates sleeves which aid in containing the medical device on the catheter, wherein the sleeves have portions comprising high modulus material to aid in the function of the sleeves.
In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient through a vessel and advanced through therein until the distal end thereof is at a desired location in the vasculature. A guidewire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guidewire sliding through the dilatation catheter. The guidewire is first advanced out of the guiding catheter into the patient""s coronary vasculature and the dilatation catheter is advanced over the previously advanced guidewire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a liquid or gas at relatively high pressures, such as greater than about four atmospheres, to radially compress the arthrosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.
In angioplasty procedures of the kind described above, there may be injury to or restenosis of the artery, which either necessitates another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To strengthen the area and help prevent restenosis, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly called a stent, inside the artery at the lesion. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter.
Stents delivered to a restricted coronary artery, expanded to a larger diameter by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer, PCT Application No. 960 3092 A1, published Feb. 8, 1996, and U.S. Pat. No. 5,007,926 to Derbyshire, the content of which is incorporated herein by reference. Palmaz et al., 156 Radiology 73 (1985) and U.S. Pat. No. 4,733,665 describe introduction of a stent over a balloon catheter.
The present invention is particularly directed to improved arrangements and configurations of sleeves for releasably covering the ends of the stent to prevent the stent ends from flaring and snagging to better facilitate delivery thereof. Examples of stent retaining sleeves can be found in Savin U.S. Pat. No. 4,950,227, U.S. application Ser. No. 09/407,836, filed Sep. 28, 1999 and U.S. application Ser. No. 09/668,496, filed Sep. 22, 2000
All US patents and applications all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention in any way, the invention is briefly summarized in some of its aspects below.
This invention concerns apparatus suitable for delivery of stents to body cavities. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel of the body of a living human or in some other difficultly accessible place. The stent prosthesis is formed of a generally tubular body, the diameter of which can be decreased or increased. Stents are particularly useful for permanently widening a vessel which is either in a narrowed state, or internally supporting a damaged vessel. Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon, to place it in a selected location in the body cavity. The present invention is particularly directed to improved arrangements for releasably covering/securing the stent, particularly the ends thereof, to the catheter to prevent snagging of the stent ends and to facilitate delivery thereof. Depending on the type of stent used, the stent is held in place on the catheter and kept from flaring upward at its end(s) by means of at least one removable end covering means, or sock, over the stent, the stent having been fitted to the catheter over the balloon, as by crimping. Most specifically, this invention is directed to improved modifications of stent retaining sleeves.
In particular, the invention is directed to an improved stent delivery system designed to hold a stent over the balloon on a catheter, via the sleeve arrangements and to protect the stent from deformation, damage or premature release during delivery intraluminally, as well as snagging during transportation. It is also a purpose of the present invention to provide for easier and smoother removal of the sleeve retaining means. The stent is formed to its lowest geometrical diameter when loaded. The sleeves of the present invention incorporate high modulus compositions in the form of bands, which are positioned over the cone portion of the balloon on top of or beneath the socks and preferably bonded thereto. The sleeves aid in retaining the stent and holds the stent to the balloon (unexpanded) with little or no relative movement between the ID of the stent and the OD of the balloon/catheter arrangement. The bands are each preferably attached (adhered or welded) to the elastomeric socks or sleeves. One end of the sleeves cover the ends of the stent and the other end of the sleeves are respectively attached to the catheter. When the balloon under the stent is inflated, the bands, which are positioned on the tapered cone portion of the balloon, are driven primarily axially, resulting in the sleeves being pushed/pulled down the balloon cones to allow the stent to deploy. The positioning of the bands on the cones of the balloon allows for more of an axial force and movement of the socks when the balloon inflates rather then a radial force and provides a flatter profile as apposed to other arrangements. This allows for a steadier, smoother, more controlled removal of the sleeves instead of an abrupt release, which may happen with a primarily radial force. Since most stents which are deformed to a low diameter will increase in diameter somewhat after being deformed (spring back), the sleeves also somewhat prevent spring back and increase the friction fit between the stent and balloon.
The present invention contemplates a stent delivery system having stent retaining sleeves having a high modulus ring or band, preferably a polymeric or metal band, located along the body of the sleeve. The high modulus band gives the sleeve improved retraction properties while allowing the stent edges to deploy. The present invention allows the stent ends to deploy at lower pressures, while assuring full retractions of the sleeves.
Modifications to this embodiment are further described below.